After the last use I scrub the gunk off with baby bottle brush, don't tell my wife, it is the only brush that reaches the right places as my son is 11 1/2months old so it has not hurt him yet!
Then dishwasher to really make them clean. For the 2L bottle I then use I starsan soak before adding canned wort and yeast. For my 1000ml flask it fits in the pressure cooker so I cook it with the foil on top and wort in it. As it is totally sterile I leave in on the counter over night before pitching the yeast stepped up in a baby food jar.