Starbucks branches have temporarily banned reusable cups in response to the coronavirus outbreak.
The coffee chain said customers would still receive a 25p discount for bringing reusable cups with them, but drinks would be served in paper cups.
Great Western Railway and LNER have banned reusable cups on trains - but GWR scrapped the policy after days.
A hygiene expert said containing the virus should be a "greater priority" than environmental concerns.
It is understood Starbucks made the decision internally, rather than on the advice of health officials.
The coffee chain's Europe spokesman, Robert Lynch, said: "Out of an abundance of caution, we are pausing the use of personal cups or tumblers in our stores across the UK.
"However, we will continue to honour our 25p discount for anyone who brings in a personal cup."
He said Starbucks was suspending its 5p charge for customers asking to use a paper cup.
Mr Lynch added the coffee chain - which, in 1998, was the first to offer users a discount for customers with reusable cups - was also introducing "increased cleaning measures" for all in-store crockery such as ceramic mugs and plates.
Starbucks stores in the US have already brought in similar measures.
The coffee chain closed half of its almost 4,300 outlets in China in January to support efforts to contain the coronavirus, which causes Covid-19.
UK train operator LNER said it had stopped accepting refillable cups on its trains "to help prevent possible contamination from handling cups and lids".
While Great Western Railway (GWR) said it banned the use of reusable cups on its trains for "three or four days" as part of "sensible precautions" to protect customers and staff.
But the train company "reverted" to its normal policy on Tuesday, a spokesman said.
He said GWR had received "a couple of comments" from people asking for an explanation of the ban.
One GWR passenger said the move was "absolutely absurd" as trains were a "germ hot spot".
Amy Slack, from Falmouth, Cornwall, said she decided against buying a coffee on a GWR train when her reusable coffee cup was declined on Monday.
"I couldn't understand what the difference was between a standard cup and a reusable cup," she told the BBC.
"We were told it's because of [coronavirus] being passed from hand to mouth… but that's the same regardless of the receptacle you're holding."
Ms Slack, 35, who works for an environmental charity, said when she asked for the reasons behind the change, staff members said they had "questioned it themselves".
"If it was government guidance I would be totally for it," she said.
"But coronavirus is going to be passed through very many more forms than reusable cups."
When asked if people should stop using reusable cups, Public Health England said its "message is clear" - that "simple hand-washing with soap for 20 seconds" was the most effective way to stop the spread of the virus.
'Not being paranoid'
At least 2.5 billion coffee cups are thrown away each year in the UK, according to a government report published in 2018.
But Prof Sally Bloomfield, from the London School of Hygiene and Tropical Medicine, said hygiene should take a "greater priority" than environmental concerns while it was still possible for the coronavirus to be contained.
"We don't know how serious [the virus] is, we are in a completely unknown phase of this, and I think in terms of preventing the spread, for the next three or four weeks then it should take a greater priority than an environmental concerns," she said.
She added the reusable cup ban was "not being paranoid".
"Handing someone a reusable cup is just the same as shaking hands with somebody. If there's anything we can do at the moment to slow down the spread, we should be doing it."
But Prof Bloomfield's colleague, epidemiologist Dr Kalpana Sabapathy, said "while things may evolve", advice to avoid the virus did not include avoiding reusable cups.
She added "one has to ask what Starbuck's objective is" since regular hand-washing "should be protocol" for workers at the coffee chain.
The Food Standards Agency's guidance for anyone working with food is to wash hands "after touching items such as phones, light switches, door handles, cash registers and money".
Greggs said there would be no changes to its reusable cup policy, where customers bringing their own cups received a 20p discount on drinks.
A spokesperson for Costa Coffee said: "We have no plans to stop allowing the use of reusable cups in our stores, but like all retailers we are monitoring the situation closely and are following government advice and guidance."
The Pret a Manger food chain did not comment.