Im almost sure there is a difference between 'warm coffee' and 'hot coffee'
As luke51991 says, we use "varm" as both "hot" and "warm". There is a word called "het (or "heit")", which means hot, but it's not used much anymore, except for describing attractive people...
In order to distinguish the level of warm we are talking, we instead combine "varm" with other words. For example, "glovarm" (glowing hot) is often used.
So, to ensure I get a steaming hot cup of coffee/tea and not a tepid or luke-warm version...how would I ask? Easter Sunday 16Apr17