Our longest service (Sunday school then the service) only lasts about 2 hours, so it's never been an issue. I eat breakfast before I go and we eat lunch pretty soon after getting home. At different points in the past, we have offered snacks between the two, but we (the church) aren't doing that now. I suppose if I had to, I could eat a little bite before going into the sanctuary, but I've never felt that it's necessary. I would feel inappropriate eating in the sanctuary. Maybe at another church, I wouldn't feel that way. Our church is slightly more formal that some that I've been in.
Any services we have at night usually only last an hour to an hour and a half, so it's not really an issue there.
Mind you we have lots of potlucks after Sunday morning service, and we feed the youth and children during their programs on Sunday nights. The youth also eat at their Wednesday night service. It seems like the youth eat everytime they get together, but their teenagers, so what do you expect.