I've just done a quick search on this topic.
It seems Trump's parents were Presbyterian especially his mother.
And once in office Trump changed his affiliation to non-denominational.
Nowhere does it say that he is Methodist.
Like many Christians switching churches, he now identifies as nondenominational
www.christianitytoday.com
Trump told Religion News Service last week in a written interview mediated by spiritual advisor Paula White-Cain that he doesn’t consider himself to be Presbyterian. He was confirmed in the church and has called himself Presbyterian numerous times over the years. But no more.
“I now consider myself to be a non-denominational Christian,” Trump said in the statement.
Trump and Hillary Clinton – rarely talk about their faith. Trump is a professed Presbyterian; Clinton a Methodist.
Trump’s attempts at public religion have been awkward, at best.
He said he does not ask for forgiveness and “does not bring God into that picture” when he makes mistakes. He has tried to put money in the Communion plate and referred to the sacrament as “my little wine” and “my little cracker.” He mispronounced a book of the Bible, and when asked about his favorite verse, has either deferred or, in one case, cited “an eye for an eye,” an Old Testament revenge scheme specifically condemned by Christ.
When asked theological questions, Trump often speaks in terms so vague they approach opacity.
Asked “Who is God to you?” by the Christian Broadcasting Network, Trump answered “God is the ultimate,” then began a brief spiel about how he got a great deal on a golf course before circling back to his original definition. “So nobody, no thing, no there’s nothing like God.”
No one has vouched for Donald Trump’s religious authenticity more than his pious and sycophantic veep. Renouncing it all now seems hypocritical.
nymag.com
“I once invited President Trump to Bible study,” Pence said in his speech. “He really liked the passages about the smiting and perishing of thine enemies. As he put it, ‘Ya know, Mike, there’s some really good stuff in here.’”
I'm not sure what qualifies someone as being Christian. Maybe anyone can claim to be one despite not seeming to know the difference between the OT and the NT, and saying their favourite passage is something that the vast majority of Christians do not claim to be a value of Christianity "Eye for an eye". Anyway, maybe he is Christian. He has said it, and maybe that is enough to qualify.