Dunno where you are, but ChariTea has a new sugar free mate. Mate based drinks in general tend to be at least less sweet then that energy drink stuff.
I personally usually just make coffee at home and take it with me, but I recognise that doesn’t work for everyone.
I just bought a used Ryzen 3 ThinkCentre as a media centre PC for 66€. Feel like the pi has a hard time competing both on price and performance in that field.