Irish wristwatch
Wicked liquid
Vicious bishops viscous biscuit
She stood on her balcony inexplicably hiccuping and amicably beconing him in
The Leith Police dismisseth us.
Red jelly, yellow jelly, red jelly, yellow jelly…
In high school drama, we did:
red leather, yellow leather
…
and others I don’t remember any more 
Back when I was much more gullible and there were so few ways to check him out on stuff, my dad said that this was the longest word he knew and that it was some kind of chemical gas or something:
diethylsulphonethylmethylmethane
Broken down into syllables, it might serve your needs:
di-ethyl-sulpho-nethyl-methyl-methane
Ot you could go with
Beep belly oten doten bo bopa deeten dotten
Supercalifragilisticexpialidocious (even though the sound of it is something quite atrocious).
I always warm up with polyethylene terephthalate.
An enemy anemone
(it took me two goes to even type that)