Finally I have something. But still if somebody see some issues with this solution please let me know:
xmlns:syncfusion="using:Syncfusion.UI.Xaml.Controls.Input"
xmlns:sync="using:Syncfusion.UI.Xaml.Controls"
<sfInput:SfNumericUpDown UpDownStyle="{StaticResource NoSpinButtonsStyle}"/>
<Style x:Key="NoSpinButtonsStyle" TargetType="sync:SfUpDown">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="sync:SfUpDown">
<Grid x:Name="PART_OuterGrid">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<ContentControl x:Name="PART_Content"
Content="{TemplateBinding UpDownContent}"
Margin="1"
HorizontalContentAlignment="Stretch"
VerticalContentAlignment="Stretch"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>