The ornamental design for a soft drinkbottle, as shown and described.
FIG. 1 is a perspective view of a first embodiment of the instant invention. The broken lines are included for the purpose of illustrating a portion of the bottle that forms no part of the claimed design; and,
FIG. 2 is a top view of a first embodiment of the instant invention. The broken lines are included for the purpose of illustrating a portion of the bottle that forms no part of the claimed design.