Towel Bathing is when someone bathes while they have a towel on. This is mostly done in Hot Springs.
801 TTS Airbats
The fourth episode of 801 TTS Airbats has Miyuki Haneda and Yoko Shimorenjaku bathing in a Hot Spring while wearing towels. Miyuki's towel is white and Yoko's towel is yellow. Arisa in the background went with no towel.
Arakawa Under the Bridge
In the second episode of Arakawa Under the Bridge, Nino bathes in a Barrel while wearing a pink towel.
In the eleventh chapter of Digimon Next, Ami Kitajima bathes in a Hot Spring wearing a towel. When she finds out that it was an illusion and that its really oil she is still wearing the towel.
In the 51st episode of the Dr. Slump remake Akane Kimidori and Tsururin Tsun bathe in a Hot Spring wearing white towels.
Neon Genesis Evangelion
The Evangelion soap trays feature each of the girls bathing in Clawfoot Bathtubs while in towels. Asuka Langley Soryu is in a red towel.
In the 58th episode of Pokemon, Misty bathes in a Hot Spring in a pink towel.
In the 40th episode of Sailor Moon, the Tsukino Family bath in a Hot Spring while in toweles. At the end of the episode, Usagi Tsukino and the other Inner Senshi bath together wearing towels, too.
In the seventh episode of Zombie-Loan, Michiru Kita bathes in a Hot Spring twice. She wears a white towel during her second bath.